- rhipicephalus sanguineus
- red campion
- red underwing
- rose moss
- rocket launcher
- ray floret
- ray flower
- rose bed
- raw throat
- respiratory tract reflex
- respiratory insufficiency
- ringdove
- ring_worm
- royal function
- radioimmunoassay
- rocking
- round_bottom flask
- rectilineal
- rectifying (a flaw error)
- ready state
- reference volume
- referendum
- reference clock
- rootlessness
- rover
- roving
- recto_vesical pouch
- rocker switch
- rheumatic heart disease
- robert venturi
- robert james fischer
- robert joffrey
- robustness index
- robustly
- reetesh
- reserve clause
- reeve
- rogues gallery
- Rogaine
- republic of venezuela
- relative crop_intensity index
- rough horsetail
- revulsion
- right of abode
- respecting
- road roller
- rib_spreader
- ribald
- raulins medium
- rehabilitation program